MRI Safety: New Cardiac Pacemaker System Now Available in the U.S.

On February 8, 2011, a new cardiac pacemaker received approval from the FDA, which for the first time allows MRI procedures to be performed in patients by following specific labeling requirements. http://www.medtronic.com/mrisurescan. The “MR Conditional” Revo MRI SureScan Pacing System from Minneapolis-based Medtronic Inc. was designed to minimize the potential interactions with the electromagnetic fields used during MRI examinations.

Comprehensive labeling information must be reviewed and adhered to ensure patient safety, and includes, but is not limited to, the following:

MRI conditions for use
A complete SureScan pacing system including a Revo MRI SureScan IPG and two SureScan leads is required for use in the MRI environment. Any other combination may result in a hazard to the patient during an MRI scan. The SureScan feature must be programmed to “on” prior to scanning a patient according to the specified conditions for use.

Clinical and pre-clinical testing has demonstrated that the SureScan pacing system is safe for use in the MRI environment when used according to the instructions in the Revo MRI SureScan Pacing System technical manual.

The SureScan pacing system can be scanned in patients under the following conditions:

1. Horizontal, cylindrical bore magnet, clinical MRI systems with a static magnetic field of 1.5 T must be used.

2. Gradient systems with maximum gradient slew rate performance per axis of ≤ 200 Tesla per meter per second (T/m/s) must be used.

3. The scanner must be in the “Normal Operating Mode.”
• Whole body averaged specific absorption rate (SAR) as reported by the MRI equipment must be ≤ 2.0 Watts per kilogram (W/kg).
• The head SAR must be < 3.2 W/kg.

4. The patient must be positioned within the bore such that the isocenter (center of the MRI bore) is superior to the C1 vertebra or inferior to the T12 vertebra.

5. Proper patient monitoring must be provided during the MRI scan. The methods include visual and verbal contact with the patient, electrocardiography, and pulse oximetry (plethysmography).

6. Patients and their implanted systems must be screened to meet the following requirements:
• no previously implanted (active or abandoned) medical devices, leads, lead extenders, or lead adaptors
• no broken leads or leads with intermittent electrical contact as confirmed by lead impedance history
• a SureScan pacing system that has been implanted for a minimum of six weeks
• a SureScan pacing system implanted the left or right pectoral region
• pacing capture threshold values of ≤ 2.0 volts (V) at a pulse width of 0.4 milliseconds (ms)
• a lead impedance value of ≥ 200 ohms (Ω) or ≤ 1500 Ω
• no diaphragmatic stimulation at a pacing output of 5.0 V and at a pulse width of 1.0 ms in patients whose device will be programmed to an asynchronous pacing mode when MRI SureScan is on

7. A health professional who has completed cardiology SureScan training must be present during the programming of the SureScan feature.

8. A health professional who has completed radiology SureScan training must be present during the MRI scan.

9. The implanted system must consist solely of a SureScan device and SureScan leads. Any other combination may result in a hazard to the patient during MRI scans.

For more information please visit http://www.medtronic.com/mrisurescan. MRI healthcare professionals are advised to contact the respective manufacturer in order to obtain the latest safety information to ensure patient safety relative to the use of an MRI procedure.

Shellock is adjunct clinical professor of radiology and medicine at the Keck School of Medicine, University of Southern California. He is also director for MRI Studies of Biomimetic MicroElectronic Systems at the National Science Foundation, Engineering Research Center, University of Southern California.

REFERENCES

http://www.medtronic.com/mrisurescan

Instructions for Use, SURESCAN MRI procedural information for Revo MRI SureScan RVDR01, CapSureFix MRI 5086MRI, Medtronic, Inc., Minneapolis, MN

Shellock FG, Woods TO, Crues JV 3rd. MR labeling information for implants and devices: explanation of terminology. Radiology 2009;253:26-30

Sutton R, Kanal E, Wilkoff BL, et al. Safety of magnetic resonance imaging of patients with a new Medtronic EnRhythm MRI SureScan pacing system: clinical study design. Trials. 2008;2;9:68.

Wilkoff BL, Bello D, Taborsky M, et al. Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment. EnRhythm MRI SureScan Pacing System Study Investigators.
Heart Rhythm. 2011;8:65-73